1. Field of the Invention
This invention relates to a liquid discharging apparatus such as an ink jet recording apparatus and a discharge recovering method therefor.
2. Related Background Art
Liquid discharging apparatus such as ink jet recording apparatus for executing recording by discharging ink toward a recording medium (recording material) such as paper cloth a plastic sheet or an OHP sheet on the basis of image information (recording information) spread as recording apparatuses having the functions of printers, copiers and facsimile apparatuses, or recording apparatuses (printing apparatuses) used as the output apparatuses of compound type electronic apparatuses including computers, word processors, etc. and work stations or the like. Also, there are various requirements for the qualities of these recording mediums, and in recent years, development for these requirements have been advanced, and use has also been made of liquid discharging apparatuses using, as recording mediums, paper (including thin paper and processed paper) which is an ordinary recording mediums and resin thin sheets (such as OHP sheets) and in addition, cloth, leather, nonwoven fabric and further, metals or the like.
The aforedescribed liquid discharging apparatuses (such as ink jet recording apparatuses) are widely applied to printers, copiers, facsimile apparatuses, etc. from the viewpoints of low noise, low running cost, ease of downsizing, ease of coloring, etc. Discharge ports (usually plural) for discharging liquid droplets (such as ink droplets) are formed in the front face of the liquid discharge head (such as ink jet recording head) of the liquid discharging apparatus, and the size of the discharge ports is of the order of several tens of microns, but recently, with a higher quality of image, the size of the discharge ports has been becoming smaller and smaller. Liquid droplets are discharged from the discharge ports on the basis of a discharge signal processed in the apparatus on the basis of liquid droplet discharge information (such as recording data) sent from a host apparatus, whereby an image (including characters and symbols) is formed on a recording medium.
In the above-described ink jet recording apparatuses for effecting recording by discharging ink from recording means to the recording medium, the ink is discharged from the minute discharge ports to thereby effect recording and therefore, clogging may occur to the discharge ports and the quality of recorded images may lower due to bad discharge (including non-discharge) and as a countermeasure therefor, it is practised to use a recovery unit for maintaining and recovering the ink discharging performance of the recording means. As this recovery unit, use is made, for example, one provided with a capping mechanism for capping the discharge ports of the recording head, suction means connected to the capping mechanism in its capping state and operating a pump to thereby generate negative pressure in the capping mechanism and suck and discharge foreign materials such as viscosity-increased ink and bubbles from the discharge ports and thereby refresh the ink in the discharge ports to thereby maintain and recover the ink discharging performance, and wiping means for wiping off foreign materials such as ink adhering to the surface of the discharge ports of the recording means.
On the other hand, in the above-described ink jet recording apparatus as the liquid discharging apparatus, in order to prevent desiccation during shipment, the interior of an ink jet head as a liquid discharging head is filled with liquid (e.g. clear ink containing no coloring material), and the technique of performing the cleaning operation (a kind of discharge recovering operation) for drawing out the aforementioned liquid to render recording (image formation) possible when the ink jet head is mounted on the ink jet recording apparatus for the first time is applied.
However, it has sometimes been the case that when the cleaning operation (recovering operation) during ordinary use is easily used to perform the cleaning operation for drawing out the liquid, impurities dissolved in the liquid (for example, additives or the like dissolved from liquid contacting materials such as a sealant and an adhesive agent) filling the head due to the severe environment during shipment are rubbed against the discharge port surface of the liquid discharging head (ink jet head) during the wiping operation in a series of cleaning operations, and the quality of a recorded image (including characters and symbols) is degraded by those impurities adhering to the ink discharging portion.
The present invention intends to perform a second suction pump operation after a first suction pump operation in initial cleaning effected to render a new head mounted on a liquid discharging apparatus for the first time capable of recording when the head is used, to thereby achieve the optionization of the cleaning operation by the first suction pump operation and thereby solve the above-noted technical problem. That is, it is an object of the present invention to provide a liquid discharging apparatus and a discharge recovering method therefor in which the optimization of the condition of the suction recovery operation can be achieved in conformity with the purpose of the initial cleaning to thereby minimize the consumption of liquid and yet minimize the time for which and the amount by which the liquid containing impurities touches the surface of discharge ports, whereby a liquid discharging head can be early and reliably subjected to the initial cleaning.
A liquid discharging apparatus according to the present invention is characterized by a mounting portion for mounting thereon a liquid discharging head provided with a discharge port for discharging liquid therethrough, a cap for covering the discharge port, suction means for effecting suction from the discharge port when the cap covers the discharge port, and control means for causing the cap to cover the discharge port when the liquid discharging head is mounted on the mounting portion, and causing the suction means, in this state, to effect first suction for effecting suction from the discharge port by negative pressure having a first negative pressure curve indicative of the relation between the negative pressure in the cap for suction and the time elapsed, and then causing the suction means to effect second suction for effecting suction from the discharge port by negative pressure in a second negative pressure curve small in the frequency of occurrence of the peak of the negative pressure per unit time as compared with the first negative pressure curve with the cap caused to cover the discharge port. According to such a liquid discharging apparatus of the present invention, the optimization of the condition of the suction recovering operation during the initial cleaning of the liquid discharging head can be achieved to thereby minimize the consumption of the liquid and yet minimize the time for which and the amount by which the liquid containing impurities touches the surface of the discharge port, whereby the liquid discharging head can be early and reliably subjected to the initial cleaning.
A discharge recovering method for a liquid discharging apparatus according to the present invention is characterized by the first sucking step of effecting, when a liquid discharging head provided with a discharge port for discharging liquid therethrough is mounted on a mounting portion for mounting the liquid discharging head thereon, suction from the discharge port by negative pressure in a first negative pressure curve indicative of the relation between the negative pressure in a cap for suction and the time elapsed with the cap covering the discharge port, and the second sucking step of effecting, after the first sucking step, suction from the discharge port by negative pressure having a second negative pressure curve small in the frequency of occurrence of the peak of the negative pressure per unit time as compared with the first negative pressure curve with the discharge port covered with the cap. According to such a discharge recovering method of the present invention, the optimization of the condition of the suction recovering operation during the initial cleaning of the liquid discharging head can be achieved to thereby minimize the consumption of the liquid and yet minimize the time for which and the amount by which the liquid containing impurities touches the surface of the discharge port, whereby the liquid discharging head can be early and reliably subjected to initial cleaning.